Eating carbohydrates contained in plants is associated with reduced heart attack and stroke risk, while eating sugar added to prepared foods and drinks is associated with increased heart attack and stroke risk. Researchers evaluated data from 110,497 healthy people who did not have heart disease or diabetes and followed them for 9.4 years (BMC Med, Feb 14, 2023;21(1):34). They found that:
• Increased total carbohydrate intake was not associated with increased risk for heart disease.
• An increase in added sugars was definitely associated with high fatty triglycerides and increased risk for heart disease and stroke.
• Substituting added sugars for sugars found IN plants (such as fruit) was strongly associated with increased risk for heart and stroke diseases.
• Substituting sugared drinks for exactly the same amount of calories in refined grains (starch) was associated with increased risk for heart disease. (Sugars in drinks raise blood sugar faster than sugars in solid foods.)
• Eating high-fiber plants was associated with reduced risk for heart disease.
• Higher plant intake was associated with significantly lower body weight, lower BMI, lower waist circumference, lower total blood cholesterol and lower LDL.
Many other studies show that you should eat carbohydrates in plants, and limit or avoid sugars added to food and drinks (PLoS One, 2015 Apr 21;10(4):e0126104; BMJ, 2020 Mar 18;368:m688; Am J Clin Nutr, 2018;107:257-267).
Carbohydrates are chains of sugar molecules. They are found in all plants and all foods made from plants. Carbohydrates can be a single sugar, or two, three or more sugars bound together. Thousands of sugars bound together are called starch, and millions of sugars bound together so tightly that you cannot break them down are called fiber.
Only single sugars can pass from your intestines into your bloodstream. When you eat, food that contains starch enters your intestines where enzymes knock off each end sugar consecutively, and each end sugar is absorbed immediately. All simple sugars and starches that are broken down in your intestines go into the bloodstream rapidly, which causes blood sugar to rise.
Fiber and other resistant starches contain long chains of sugars that cannot release their end sugars, so they are not absorbed. They pass to the colon where bacteria convert them into fatty acids that help to prevent colon cancer and heart attacks. A healthful diet has lots of carbohydrates that release their sugars slowly, and lower amounts of carbohydrates that release sugars rapidly. The easier it is to break carbohydrates down into single sugars, the higher your blood sugar level rises and the more insulin you produce.
Refined Carbohhydrates and Slowly Digested Carbohydrates
Most refined carbohydrates are ground-up whole grains (flour) or sugars that have been extracted from high-sugar plants (sugar cane, sugar beets, corn, fruits and so forth). The most healthful carbohydrates are those left with fiber where nature puts them: in whole grains, beans, nuts and other seeds, vegetables and fruits. The most unhealthful carbohydrates are foods made from refined carbohydrates: flour, white rice, milled corn, fruit juices and all extracted sugars.
Whole grains are seeds with a starchy middle that is covered with a thick fiber coating like a capsule. When you eat whole grains, this capsule prevents sugar from being released and blood sugar levels do not rise very much. When whole grains are refined, the outer coating is stripped away and the starchy middle is ground into a powder to make flour, so it no longer has the protective capsule that keeps it from being broken down so quickly. You get a high rise in blood sugar that calls out large amounts of insulin.
Refined carbohydrates are quickly absorbed in the upper intestinal tract to increase risk for obesity and diabetes. On the other hand, slowly digested or non-absorbable carbohydrates are slowly absorbed in the colon so they help to lower cholesterol and prevent diabetes and heart attacks (American Journal of Clinical Nutrition, 2000;72(6):1461-1468). If you are diabetic or trying to lose weight, you don’t need to avoid all carbohydrates, but you should limit or avoid refined carbohydrates that cause a high rise in blood sugar.
Look for Hidden Sugars
The average North American takes in 150 to 200 pounds of sugar a year. Most of your sugar intake comes from added sugars in drinks and in packaged, frozen or canned foods that you buy in grocery stores or eat in restaurants. More than 75 percent of the packaged foods in your grocery store have added sugar in them. Many of these foods do not taste particularly sweet, so you don’t even realize that you are eating sugars. Check the foods you buy for hidden sugars, such as:
• salad dressings and BBQ sauces
• frozen and microwave meals
• canned fruit
• breakfast cereals
• peanut butter and other nut butters
• packaged diet foods
• power bars, energy bars, diet bars and “health” bars
• bakery products
• dairy products and non-dairy milks
• fruit-flavored drinks and soft drinks
• many alcoholic drinks including wines
A healthful diet for everyone includes plenty of vegetables, fruits, whole grains, beans and other seeds. If you are trying to lose weight or are diabetic, you should restrict refined carbohydrates and foods that cause high rises in blood sugar:
• foods made from flour
• all drinks with sugar in them including fruit juices
• all foods that contain added sugars
Even if you are not trying to lose weight, I recommend limiting these foods to keep from gaining the ten pounds or more that most people add with each passing decade.
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe’s full bio.